TTN and familial dilated cardiomyopathy: Most notable is TTN, an enormous scaffolding protein of the sarcomere, which contributes the most cases of DCM.28,29 For HCM and ARVC, TTN was classified as limited.14LMNA, encoding a protein of the inner nuclear membrane that exhibits striking pleiotropic effects in skeletal muscle, adipose, and other tissues, was considered definitive for DCM but limited for ARVC.